With recent tendency toward non-coating finish of automotive interior trims such as instrument panels for the purpose of reducing the production costs, there are rapidly growing demands for developing interior parts having excellent appearance such as good weld appearance and low gloss giving relaxed feeling by preventing light reflection. Also, the demands for safeguard and low-cost materials are coming more severe. In addition, the recent tendency to produce whole parts of instrument panels from the same material creates demand for materials well-balanced in impact resistance and stiffness so as to meet the performance requirements of any parts of instrument panels.
Conventionally, low-cost, general-purpose propylene-based resins have been widely used as materials for automotive interior trims. It is known that the impact resistance (room-temperature Izod impact strength) of propylene-based resins can be effectively improved by blending a styrene-based elastomer. However, the use of styrene-based elastomer causes problems such as increased production cost and high gloss of molded articles.
As molding materials having an excellent low-temperature impact resistance, there have been proposed, for example, a resin composition obtained by blending a crystalline propylene-ethylene block copolymer with an ethylene-α-olefin copolymer produced in the presence of a metallocene catalyst (Japanese Patent Application Laid-Open Nos. 7-145272 and 7-145298); a resin composition obtained by blending a propylene-based resin with an ethylene-butene-1 copolymer having a relatively large butene-1 unit content (produced substantially in the presence of a metallocene catalyst) (Japanese Patent Application Laid-Open Nos. 6-192506 and 7-18151); and a resin composition obtained by blending a propylene-based resin with an ethylene-octene-1 copolymer having a relatively large octene-1 unit content (produced substantially in the presence of a metallocene catalyst) (International Publication No. WO94/6859). These resin compositions exhibit a good low-temperature impact resistance, but fail to produce molded articles having a sufficiently low gloss.
Thus, the propylene-based resin compositions used as materials for automotive interior trims are required to simultaneously satisfy the antinomic characteristics, i.e., mechanical properties such as impact resistance and stiffness and external appearance. The conventional propylene-based resin compositions have been improved in the balance of these properties to some extent, but are still unsatisfactory.